The phylum Platyhelminthes consists of mainly flatworms, such as planaria, tapeworms and flukes.
Platyhelminthes are invertebrates, and have bilateral symmetry.
They are the first phylum to introduce three types of body layer cells: endodermic, mesodermic and ectodermic providing them with a more complex muscular system, excretory system and reproductive system. The phyla before this, Cnidarians, only had two layers
Acoelomates. The three layers of tissue are touching.
Gastrovascular body plan.
Tapeworms are parasites that infect an organism's digestive tract, causing discomforting symptoms such as anemia, diarrhea, loss of appetite, seizures, and headaches.
Flatworms are flat due to an undeveloped respiratory and circulatory system, and take in oxygen through diffusion.
Flukes leech nutrients off of other organisms most commonly in the digestive system or liver. At times they travel to other organs such as the heart or the lungs when ingested.
Planaria have the ability to regenerate when severed.
external image Acoelomate.JPG
Diagram of flatworm body plan (those eyes scare me)
detailed structure of planarian anatomy
Diagram of flatworm body cells
external image 250px-A-ferox_digenean1.jpg
Picture of a fluke that infects fish
File:Tenia solium scolex.jpg
Tapeworm
Why are Platyhelminthes flat?
A) Because they are invertebrates
B) Because they are acoelomates
C) Because they lack a respiratory system so they have to absorb their nutrients
D) Because they can infect their host more easily
Diagram of flatworm body plan (those eyes scare me)
Diagram of flatworm body cells
Picture of a fluke that infects fish
Tapeworm
Why are Platyhelminthes flat?
A) Because they are invertebrates
B) Because they are acoelomates
C) Because they lack a respiratory system so they have to absorb their nutrients
D) Because they can infect their host more easily